The present invention relates to attachments for valve spring depressing tools and more particularly to such an attachment that facilitates depression of valve springs within deep recesses within an engine cylinder head.
It is common with modern four cylinder automotive engines that the valve train assembly be of the "overhead cam" configuration. With such an arrangement, the operational valve cam is rotatably mounted at the top of the engine cylinder head. The cam lobes directly engage followers mounted to the valve assemblies. This arrangement increases engine efficiency by eliminating the push rod and rocker arm assemblies typical in older, larger engines.
In order to keep weight and size at a minimum, the cam is journalled at the very top of the engine head and the valve stems are set within relatively axial recesses in the cylinder head casting. Access to the valve springs and associated elements is therefore hindered.
The typical valve assembly includes a spring or two concentric springs that operate against the valve stem to hold the valve head in a closed position. The cam, working against the spring, causes the valve stem and head to move downwardly, opening the adjacent intake or exhaust port. The valve stem is connected to the return springs through a keeper assembly that must be removed to allow removal of the valves from the cylinder head. The keepers must also be removed if the valve springs are to be removed for replacement or testing.
To facilitate removal of the spring keepers, a special tool has been developed which resembles a "C clamp". A threaded member at one end of the clamp is positioned in engagement with the valve face at the bottom of the valve. The remaining end of the clamp includes a spring engaging "jaw" attachment that sets against the spring but does not engage the valve stem. Tightening of the clamp assembly causes depression of the spring and results in exposure of the keepers. "C clamp" type depressing tools are very effective for older model engines where the valve springs are exposed and easily accessible. They do not work effectively on the smaller engines where the valve springs are set within axial recesses in the cylinder head. The spring engaging attachments will not reach down into the recess to engage the spring.
Unsuccessful attempts have been made to provide a serviceable attachment to the conventional "C clamp" spring depressing tools that would permit their use in such situations. For example, "Duro-chrome" tools of Duro Metal Products Company, Chicago, produce a "medium offset jaw" that will attach to the "C clamp" spring depressing tools for use in overhead valve engines. However, the offset jaws are integral with the bracket which mounts them to the "C clamp" arrangement. The offset is, by experience, insufficient to position the spring engaging jaws deeply enough within many of the current engine cylinder heads. Furthermore, the integral nature of the jaw and bracket often interferes with finger access to the valve keepers within the narrow confines of the cylinder head recess.
Another unsuccessful attempt at a solution to the above problem was to do away entirely with the "C clamp" spring depressing tool and make use of a lever depressing device. With this arrangement, the engine cylinder head must be secured to a flat plate. The plate, in turn, is secured to a work bench. A bar extending the full length of the cylinder head is then bolted to the top surface of the head. A lever arm is pivoted to the bar and includes a spring depressing member mounted thereto.
Downward forceful movement against the outward end of the bar will move the spring depressing member into contact with the valve return springs and depress them, exposing the keepers and top end of the valve stem. The mechanic must hold the lever down with one hand while removing the keepers from the valve stem with his free hand. This can be a dangerous and at best a very cumbersome process, often resulting in one of the keepers falling from the stem further down into the head recess.
It is much more desirable to make use of a device such as the "C clamp" depressing tool or some other form of valve return spring depressing tool that permits use of both hands to gain access to the valve keepers or elements associated therewith.
The present invention is an attachment that mounts easily to existing "C clamp" arrangements or can be used with an independent tool for depressing and holding valve return springs in a depressed condition while simultaneously allowing maximum access to the exposed area of the valve for both of the mechanic's hands. A single offset leg extends downwardly into the depression, with a ring mounted at the bottom end of the leg to engage and depress the spring. The top of the valve and the keepers become exposed as the spring is depressed. Access is maximized by the offset leg which can also be pivoted about an upright axis to assure easy access to the keepers or associated elements.